[Elecraft] K2 PLL reference oscillator range test

[John, KI6WX]

Adam;
I'm the person who designed the thermistor PLL stability circuit for the K2.
This circuit is included in all new K2's and older ones may be updated by
ordering a mod kit from Elecraft.  It is my professional opinion that a PLL
tuning range between 9.8 kHz to 15 kHz is fine and will not impact the
performance of the PLL reference oscillator.  The various Xtals that I
tested in designing this circuit last winter showed a variation between 12
and 13 kHz as the Xtal is changed.  Variations in L31 could cause a slightly
larger range.  The tuning range must be above 9.8 kHz or the K2 will not
tune correctly on 160 meters.

The Elecraft manual will be updated to reflect the 9.8 to 15 kHz range.  If
someone has a PLL tuning range above 15 kHz, we do want to know about it
because it would imply that some of the components in this circuit are
varying more than they should.

-John
 KI6WX

----- Original Message ----- 
From: <akern@haverford.edu>
To: <elecraft@mailman.qth.net>
Sent: Sunday, June 29, 2003 1:55 PM
Subject: [Elecraft] K2 PLL reference oscillator range test


> Another question:
>
> I just started running through the Part II assembly tests and alignments.
> I couldn't do the 4 MHz oscillator calibration because I don't have my
> external frequency counter on hand.  I then went on to the PLL reference
> oscillator range test and got a range value of 13.8 kHz.  The value
> should be between 9.8 and 13 according to the manual.  Is a value of 13.8
> going to be problematic?  Could I be getting an artificially high value
> because I have not yet trimmed C22 as part of the 4 MHz oscillator
> calibration?  I am going to recheck all of the joints in the PLL circuit
now.
>
> Happy field day!
>
> -Adam, N1KO
>